1. Field of the Invention
The present invention relates to filters and filter housings. More particularly, the present invention relates to a disposable box filter useable in medical and other applications which is of low cost and capable of being made absolutely sterile before use.
2. Description of the Prior Art
Box filters, because of their unique configuration, low cost, and ease of manufacture, have been found very useful in medical applications, as well as in other applications. It is quite important in medical applications that a filter be capable of being made absolutely sterile before use. To avoid the necessity of cleaning and sterilizing operations after use, it is also desirable that the filter be disposable. For a filter to be disposable, it must necessarily be of low cost. Many attempts at making a true, low cost, disposable box filter have been found in the prior art. None of them have been entirely successful.
One such prior art patent is the U.S. Pat. No. 3,765,537. While this filter is satisfactory in use, it has significant limitations which arise during the manufacturing process. The filter sheet is held tightly between an internal wall and a top wall of the filter housing and is bonded in place. This requires an open pore filter sheet. This limits the type of filter element that can be used in the housing, and also increases the manufacturing cost.
Another such attempt in the prior art is shown in U.S. Pat. No. 3,815,754. In an attempt to eliminate the limitations imposed by having to bond through open pores of the filter sheets, this patent attempts simply to pinch the sheet between an inner wall of the housing and the ends of a pair of vertical walls. While this design eliminated the limitation on the type of filter element that could be used to obtain a sufficient seal, the resultant filter was found not suitable for use at relatively high pressure differentials.
In an attempt to solve the problems of the prior art still present after the inventions disclose in U.S. Pat. Nos. 3,765,537 and 3,815,754, the filter shown in U.S. Pat. No. 4,187,182 was developed. In this patent, the filter sheet is pinched between the edge of the inner side walls and other portions of the housing. However, this filter increases manufacturing expense by requiring the pleats of the corrugated filter element to be trimmed specially at positions midway of the height of the filter element, thus increasing greatly the manufacturing costs.
Thus, those skilled in the box filter art continued to search for a solution to the problem of providing a truly low cost disposable box filter.